Control of fluid compressor systems



Sept. 28, 1943. A. G. KERSHAW ET AL I CONTROL OF FLUID COMPRESSOR SYSTEMS Filed Dec. 3, 19 51 INVENTORS %VF\EENWOOD KE RSHAW IBLLIAM SIMMONS 4 ve- ATTORNEY Patented Sept. 28, 1943 2,330,364 l CONTROL OF FLUID COMPRESSOR 'sgisrEMs Arthur Greenwood Kershaw and Arthur William Simmons, Kings Cross, London, England, as-

signors, by

house Air Brake Company,

mesne assignments, to Westing- Pittsburgh, Pa., a

corporation of Pennsylvania Application December 3, 1941, Serial No. 421,458

In Great Britain September 3,1940 7 9 Claims. (Cl. 303-1 1) This invention relates to the control of fluid compressor systems of the kind in which a number of power-operated compressors are arranged to efiect the-supply of compressed fluid to a common receptacle such for example as the main reservoir of a fluid pressure braking system, each compressor being provided with an automatic governor device responsive to the pressure obtaining in the receptacle and adapted to render the compressor operative or effective to supply compressed fluid to the receptacle when the pressure therein falls below a predetermined value.

In order to distribute the load evenly between the several compressors of the system it is evidently desirable that the automatic governor devices should start their respective compressors into effective operation substantially simultaneously in the event of the pressure in the receptacle becoming reduced to the predetermined value and although this result can be attained by suitable adjustment of the governor devices, this adjustment must evidently be made with a relatively high degree of precision in order to ensure the desired synchronisation of the compressors.

The invention has for its object toavoid the necessity-for the accurate adjustment of the governor devices above referred to and according to the principal feature of the invention the controlling pressure acting upon each of the governor devices is arranged to be automatically and temporarily reduced when the pressure in a portion of the fluid pressure system is varied so as subsequently or ultimately to incur a fall of pressure in the receptacle which must be restored by the action of the compressors.

Each of the governor devices while remaining under the permanent control of the pressure in the receptacle is thus temporarily caused to operate to render its compressor effective and all the compressors are thus brought into at least temporary operation .at'the same time. The invention is illustrated by way of example in the accompanying drawing, Figure 1 of which is a diagrammatic view partly sectional of a preferred form of control apparatus embodying the invention, Figure 2 being a similar View of a modified portion ofthe apparatus of Figure 1.

Referring now to'the drawing the invention is illustrated asappliedto a fluid pressure braking system for a train of railwayvehiclescomprising the usual main reservoir and adapted to be supplied with fluid under pressure from a I number of compressorsat different points along the train each adapted to supply compressed air to the reservoir through a main reservoir train pipe I andea'ch provided with an automatic gov ernor device 2 responsive to the main reservoir train pipe pressure to control the operation of the associated compressor which is arrangedto be'mechanically driven from the vehicle on which it is mounted; v In actual practice, such fluid pressure equip ments differ somewhat, according to" the type of service for'which they are designed. By way of example, specific systems embodyingv more than one compressor controlled by individual gov ernors and operable to supply a common pipe are disclosed in the United States Patents 1,060,650 to Turner, May 6, 1913, and1,175,0 l7to Clark, March 14, 19161 1 The control chamber of the governor device 2 to which fluid is supplied at the pressure of the main reservoir so as to control the action of the device is'arranged to be in permanent communi-" cation with the main reservoir pipe I through asuitable restricted orifice or choke? and the control chamber on the governor side of the choke 3' communicate's through a pipe 4 with a synchronising valve device e a The valve device 5 comprises '(in'theform shown in Figurel) a casing 6' containing a valve chamber 1' communicating with the control chamber of the governor device through the pipe 4 together with a bulb or venting chamber 8 of suitable-relatively small capacity.

The valve chamber 1 contains a slide valve 9 adapted in one portion (viz. that shown in' Figure landhereinafter termed the normal position) to establish communication through a cavity 1B in th slide valve 9 between the bulb 8 and an exhaust chamber ll leading tothe atmos-' phere through a port l2 and in another 'position (hereinafter termed the venting position) to out 01f communication between the bulb 8 and the exhaust chamber I I and to establish communication between the bulb 8 and the valve chamber I. The slide valve 9 is-provided with an operating stem I3 projecting into the exhaust chamber-l l and operatively connected to a .mov-

able piston I4 adapted to slide in a control cylinder 55 forming an extension of the exhaust chamber I I; A suitable spring It in the exhaust chamber II acts upon the piston IB and tends to maintain it in a normal position in which the slide valve 9 is also in its normal position shown. The control cylinder I on the inner side of the piston It is in permanent communication with a brake cylinder of the vehicle through a pipe II, the operation of the apparatus being as follows:

Under normal conditions with the brake cylinder at atmospheric pressure since the brakes are released, the piston I4 and slide valve 9 of the synchronising valve device 5 are maintained in their normal positions shown in Figure 1 by the spring I6, so that the bulb ii'is at atmospheric pressure due to its communication with the exhaust chamber II through the cavity II) in the slide valve 9.

When an application of the brakes is eifected the brake cylinder pressure in the control cylinder I5 acting upon the piston I4 moves the latter against the action of the spring I6 to move the slide valve 9 to its venting position. Fluid under pressure is thus released from the control chamber of the automatic governor device to the bulb 8 through pipe 4, valve chamber-5 and a port I8 which is uncovered by the slide valve 9 when the latter is in its venting position. As a result the pressure in this control chamber is correspondingly reduced and the governor device 2 is caused to operate to render the corresponding compressor operative.

As soon as the pressures in the control chamber and the bulb 8 equalise, fluid will be supplied through the choke 3 to restore the control chamber pressure to main reservoir pressure and as soon as the latter pressure has been restored to its normal value after the braking application by the action of the compressor, the governor device 2 will operate again to render the compressor inoperative.

The synchronising valve device 5 thus does not permanently affect the action of the governor device 2 in controlling the operation of the compressor in response to variation in the main reservoir pressure.

As soon as the brakes are released, the spring I6 will restore the piston I4 and slide valve 9 to their normal positions cutting off communication between the valve chamber 1 and the bulb 8 and venting the latter to the atmosphere.

In the case of a braking system of the automatic type comprising triple valves controlled by an automatic train pipe and control cylinder I5 of the synchronising valve device 5 may be arranged to communicate with the triple valve exhaust so that the valve devices will only operate as above described to render the compressors effective when the brakes are released and the triple valves move to their release positions.

In the alternative arrangement shown in Figure 2, the control cylinder of the synchronising valve device is arranged to be in communication with the automatic train pipe through a pipe I9, the piston I6 of the valve device 5 being maintained in the normal position shown against the opposing action of the spring I6 by the train pipe pressure. In this position of the piston I4 the slide valve 9 operated thereby is arranged to occupy its normal position, bein'g'moved to its venting position by the action of the spring I6 whereas the train pipe pressure is reduced to effect an application of the brakes.

The invention may also be applied tobraking systems of the vacuum type which also comprise apparatus operated by compressed air such for example as sanding device, throttle valve control mechanism and whistles. In this case the control cylinder I5 is arranged to be subject to the vacuum obtaining in the brake pipe and the synchronising valve device is suitably modified by arranging for the control spring to act upon the piston in opposition to the vacuum in the control cylinder I5.

It will be evident from the above description that the pressure or vacuum obtaining in any part of the system and which, when varied involves the compressors being subsequently rendered operative may be utilised for controlling the action of the synchronising valve device.

Furthermore the choke 3 above referred to may be introduced at any suitable point between the control chamber of the governor device 2 and the receptacle to be replenished and other unrest-riot ed paths of communication between these elements may be also provided if desired.

It will now be seen that, by providing an auxiliary local vent valve in association with the pressure controlled governor of each of several compressors supplying air to a main reservoir in a fluid pressure brake system, together with common control means for actuating each vent valve in response to a braking operation resulting in a reduction in main reservoir pressure, substantially equal distribution of the work between the compressors will be ensured, since each compressor will always be set in operation by reason of the limited local reduction in pressure at the associated governor, with the result that all the compressors will be operated together to restore even minor withdrawals of air from the main reservoir.

The invention is thus by no means limited to the particular arrangements or applications above described and illustrated by way of example and variations in these and other respects may obviously be made without exceeding the scope of the invention.

Having now described our invention, what we claim as new and desire to secure by Letters Patent is:

1. In a fluid pressure system of a type comprising a pressure pipe adapted to receive fluid under pressure supplied by a compressor, and an automatic governor device responsive to a reduction in the pressure of fluid in said pipe for controlling the operation of the compressor, in combination, a flow restricting device interposed between said governor device and said pipe, and means connected in the system on the governor side of said flow restricting device and responsive to a variation in the pressure of fluid in another part of the system for efiecting a temporary reduction in the pressure of fluid acting on said ggvernor device, and consequent operation there- 0 2. In a fluid pressure system of the type comprising a pipe adapted to receive fluid supplied under pressure by a compressor, and an automatic governor device responsive to a reduction in the pressure of fluid in said pipe for controlling the operation of the compressor, in combination, a flow restricting device interposed between said governor device and said pipe, and means connected in the system on the governor side of said flow restricting device responsive to the variation in the pressure of fluid in another part of the system for efiecting a predetermined fixed temporary reduction in the pressure of fluid acting on said governor device, whereby operation thereof is initiated.

3. 1m a fluid pressure system of the type comprising a storage reservoir pipe. which receives fluid supplied under pressure by a compressor,

and an automatic governor deviceresponsive to a reduction in the pressure of fluid in said'pipe for controlling the operation of the compressor, in combination, a flow restricting device interposed between said governor device and said pipe, a normally vented chamber, and means connected in the system on the governor side of said flow restricting device responsive to a Variation in the pressure of fluid in another part of the system for venting fluid under pressure from said governor device to said chamber to eiTect the operation of said governor device.

4. In a fluid pressure system of the type comprising a storage reservoir pipe arranged to receive fluid supplied under pressure by a coinpressor, and an automatic governor device responsive to a reduction in the pressure of fluid in said reservoir pipe for controlling the operation of the compressor, in combination, a flow restricting device interposed between said governor device and said reservoir, a normally vented chamber, and means connected in the system on the governor side of said flow restricting device responsive to a variation in the pressure of fluid in another part of the system for venting fluid under pressure from said governor device to said chamber to effect operation of said governor device, said means being operative upon a subsequent different variation in the pressure of fluid in said other part of the system for cutting off the communication from said governor device to said chamber while establishing a communication through which fluid under pressure is vented from the chamber. i

5. A fluid pressure system comprising a reservoir pipe for receiving fluid compressed by a compressor, automatic governor means associated with said reservoir pipe, said governor means being responsive to a reduction in the pressure in said reservoir pipe for starting said compressor, and an auxiliary control device connected to said reservoir pipe at a point close to the governor means, said control device including a normally Vented chamber, actuating means responsive to variations in an operating pressure, and valve means operable thereby to establish communication from said pipe to said chamber for effecting limited local reduction in fluid pressure in said reservoir pipe, whereby said governor device will be set in operation upon variation in said operating pressure regardless of the pressure in said pipe.

6. In a fluid pressure system comprising a reservoir pipe for conducting fluid under pressure from one or more compressors to a reservoir, in combination, pressure responsive compressor governor'means'connected to said reservoir pipe, a choke in said pipe, and a synchronizing valve device interposed between the choke and the gov ernor means, said valve device being operative in response to an actuating limited local \reduction in the pressure in said p p 7 7. In a fluid pressure system, in combination, a reservoir pipe for receiving fluid compressed by a compressor, a branch pipe having a restricted but always open communication with said reservoir pipe, automatic governor means responsive to reduction in the pressure in said branch pipe for starting said compressor, and an auxiliary control device connected to said branch pipe, said control device including a casing having a normally vented bulb, a piston subject to a variable operating pressure, and valve means operative by said piston upon pressure for establishing communication between said bulb and said branch pipe, whereby limited local reductions in the pressure in said branch pipe can be effected for rendering said governor means operative in response to variations in said operating pressure.

8. In a fluid pressure brake system, in combinatioma main reservoir pipe, an extension pipe connected thereto by way of a restricted com munication, automatic compressor governor means normally responsive to pressure in said extension pipe, auxiliary control valve means connected to said extension pipe and operable to eifect a sufiicient local discharge of fluid there from to set said compressor governor means in operation, a brake cylinder pipe, and fluid pressure operated means responsive to an increase in pressure in said brake cylinder pipe for actuating said control valve means.

9. In a fluid pressure brake system, in combination, a main reservoir pipe, an extension pipe,

connected thereto by way of a restricted communication, automatic compressor governor means normally responsive to pressure in said extension pipe, aux liary control valve means connected to said extension pipe and operable to eflect a sufllcient local discharge of fluid therefrom to set said compressor governor means in operation, a normally charged branch pipe communicating with the brake pipe of said fluid pressure brake system, and fluid pressure operated means responsive to a reduction in the brake pipe pressure in said branch pipe for actuating said vent valve means.

ARTHUR GREENWOOD KERSHAW.

ARTHUR WILLIAM SIMMONS.

pressure to-effect a variation in said operating 

